Method for treating barium toxic water using low-temperature stabilized polyacrylamide compositions

ABSTRACT

Aqueous compositions for the treatment of barium-toxic waste waters are provided. The compositions, which are storage stable at freezing temperatures, include ammonium sulfate and an agent for in situ coagulation of non-ionic barium in the form of environmentally safe solid phase particulates.

REFERENCE TO RELATED APPLICATION

This application is a continuation-in-part of my co-pending applicationSer. No. 276,857, filed June 24, 1981, now abandoned.

TECHNICAL FIELD

This invention relates to the treatment of waster waters for purposes ofenvironmental safety and more particularly relates to compositions forthe treatment of barium-toxic waste waters.

BACKGROUND OF THE INVENTION

Waste waters entering the environment from industrial operations, metaltreating, mining, and the like are commonly subject to contamination byvarious undesirable ionic substances. Waste waters containing ionicbarium, for example, must be treated with soluble sulfate before theycan be allowed, substantially free of barium, to enter ground waters orrivers (see, for instance, James et al, Water Treatment, page 204, CRCPress, 3rd Ed., Cleveland, 1966). Barium is not a common contaminant ofwater. However, a concentration in excess of one part per million (ppm)is objectionable because of the seriousness of the toxic effects ofbarium on the heart function, blood vessels, and nerves (Zajic, WaterPollution, Disposal and Reuse, page 13, Marcel Dekker Inc., New York,1971). Chemical compositions used for treating waste waters areordinarily made up in concentrate form and in this form aredispenser-packaged and kept in stock until ready for use. However, inthe case of aqueous concentrates kept in stock for long periods, thesame often undergo freezing and thawing, crystallizing, oxidation,settling out, etc.

It is therefore an object of the present invention to provide storagestable aqueous compositions for the treatment of barium-toxic wastewaters.

It is another object of the invention to provide aqueous compositions ofthe type described which are storage stable in cold weather, even attemperatures below the freezing point of water, i.e., 32 degrees F.

These and other objects, features and advantages will be apparent fromthe following description and claims.

SUMMARY AND DETAILED DESCRIPTION

Briefly stated, the invention concerns a non-viscous aqueous compositioncontaining ionic sulfate for the treatment of barium-toxic waste waters.The term "non-viscous" as applied to the aqueous composition of theinvention means that the composition is an aqueous liquid havingsubstantially the same viscosity as water alone. The composition inparticular comprises in solution ammonium sulfate and a water miscibleagent for coagulation or flocculation of non-ionic barium in the form ofnon-toxic or environmentally safe solid-phase particulates, the ammoniumsulfate being present in a concentration such that the composition isstorage stable at temperatures below 32 degrees F. The composition ofthe invention is particularly useful for the precipitation and removalof barium chloride from waste water by a batch procedure using simpleequipment as will be presently described. As used herein, the term"barium-toxic waste waters" refers to waters which contain solublebarium in a concentration appreciably more than one part per million; infact, the concentration of barium chloride in wash/waste water from somesources such as metal heat treating plants typically may be in the rangeof 0.1-1.5% by weight. In a preferred form, the composition of theinvention may contain a rust preventative or anti-oxidant such as sodiumnitrite, sodium borate (borax), triethanolamine, oxidized petrolatum(e.g., ALOX 1843 available from ALOX Corporation) and the like. Theamount of ammonium sulfate used in the composition is subject toconsiderable variation. In general, one uses an amount which is solubleover a wide temperature range and sufficient to enable prompt settlingout of barium (as insoluble sulfate) in waters treated with thecomposition. A preferred range of concentration is about 15% to about40% by weight of ammonium sulfate, a concentration of about 20% byweight being used for best results. When mixed with waste water, thecoagulation agent or flocculant present in the subject compositionserves in situ to convert or coagulate the resulting barium sulfateprecipitate from what would be an ultrafine nonfilterable particulateinto a solid form which is sufficiently large that it quickly settlesand can be readily separated (for safe disposal) as an acid insolublesolid waste, as by decanting, centrifugation, and/or filtering. For thispurpose, the choice of coagulant is not critical. Any of a wide varietyof coagulants and flocculant preparations are suitable. Polyacrylamidepolymer is used in a concentration of at least 5 ppm. Preferredcoagulants which are commercially available are, for example, Hercofloc®831.2 and 847, supplied by Hercules Inc., Wilmington, DE 19899; alsoNalco® 7763, 7744-A, and 8800 and Nalcolyte® 607 and 670, supplied byNalco Chemical Co., Oak Brook, IL 60251; for a comprehensive list ofsuppliers, see Chemical Week 1970 Buyers Guide, page 484, McGraw-Hill,New York.

The invention in another preferred aspect concerns the method oftreating barium-toxic waste water comprising mixing an aqueouscomposition according to the invention with the waste water in an amountsufficient to enable prompt settling out of barium as solid phaseparticulates in the thus treated water and separating the particulatesfrom the water as solid waste.

The invention is illustrated by the following examples.

EXAMPLE 1

Fifteen gallons of an aqueous 20% ammonium sulfate composition fortreating barium-toxic waste water are made up in three 5-gallon portionseach of which is formulated from the following components listed in theorder of addition:

    ______________________________________                                                                  Parts by                                                              Grams   Weight                                              ______________________________________                                        Water               17351.40  78.87                                           Rust inhibitor:                                                               NaNO.sub.2          151.36    0.69                                            Na borate.10 H.sub.2 O                                                                            65.12     0.30                                            Coagulant, polyacrylamide polymer                                                                 32.34     0.15                                            (Hercofloc 831.2)                                                             Ammonium sulfate    4400.00   20.00                                           ______________________________________                                    

Each of the solid components when added is thoroughly mixed until it isdissolved. Each gallon of the resulting composition removes 2.97 poundsof barium chloride from waste water. It is particularly useful for heavyduty applications such as removal of barium contained in rinse waterfrom a metal parts heat treat line. In a typical operation, forillustration, a heat treat line may consist of a series of baths such aspreheat, hi-heat, and barium salt quench stations and water rinse bathsfor the parts being processed and also for the fixtures carrying theparts through the line. This wash water becomes contaminated withvarious chemicals including barium chloride (typically 0.1-1.5% byweight) and must be treated to remove the barium before disposal. Forholding purposes, the waste water is pumped into storage tanks and helduntil treated for removal of toxic components. For a heat treat linerunning two or three shifts and disposing of the stored rinse water onceeach week, the capacity of each storage tank conveniently may be 400gallons. In a typical set-up, two tanks (fiber glass filledthermosetting plastic, 4-foot diameter, open top cylindrical) are usedin tandem, one in operation and the other on stand by. The connectingpipe work and valves are inert plastic; the bottom of each tank is aninverted cone shape with a drain at the cone apex, accessible fordrainage directly to a 55-gallon drum beneath the tank. A second drainabove the cone in the cylindrical section interconnecting the two tanksallows the solid-free treated water in each tank to be decanted fromsludge in the respective tank. Each tank is fitted with an electricpropeller mixer with a 6-8" impeller rated at several hundred rpm. Theprocedure for removing barium from the waste water collected in a fulltank (at room temperature) is to add 10 gallons of the aqueouscomposition of Example 1 with stirring for 30 minutes. The stirring isthen stopped, and the resulting barium sulfate precipitate is allowed tosettle. A clean one-liter sample of the supernatant is then taken, and asmall amount of Example 1 composition is added without mixing. Formationof a white precipitate indicates that removal of barium is not completein which case the remainder of the third 5-gallon lot of Example 1composition is added with stirring for 30 minutes and the mixture isallowed to settle. In a typical case, the barium ion level of an aliquotof the resulting solid-free wash may be 100 ppm or less. Treatment ofthe wash water can be repeated, if desired, to reduce the barium leveleven farther or the wash water can be drained through the side outlet tothe sewer and the solid sludge containing barium can be discharged aswaste.

An alternative procedure for treating the wash waste and for reading the"zero"-barium end-point is as follows:

Take a 1000-ml. aliquot of wash water to be treated in a beaker. AddExample 1 composition in steps of 1 ml. After each addition, stirvigorously and then allow the precipitate to settle for at least 2minutes. Without stirring, add the next 1 ml. of the composition. If nowhite precipitate is formed in the clear supernatant liquid, asufficient amount of the composition has been added. Note this amount.If white precipitate is formed, stir vigorously and allow to settleagain. Add the next 1 ml. of the composition and repeat the aboveprocedure until no more white precipitate is formed. Knowing the volumeof waste water to be treated and using the above relationship, the totalamount of Example 1 composition needed can be calculated as follows:##EQU1##

Illustration:

If a 1000-ml. sample of wash water requires 9 ml. of Example 1composition and 400 gallons of wash water are to be treated, the amountof Example 1 composition needed is ##EQU2## The amount of Example 1composition necessary is added slowly while the treating tank isagitated. Agitation should be continued for 30 minutes after theaddition to assure that all barium chloride has reacted. The agitator isthen stopped to allow the precipate to settle to the bottom. The bariumsulfate precipitate is disposed as solid waste, and the clear top layercan be discharged into a sewer. Large treating tanks may require severalhours to settle. This settling period can be eliminated or reduced byremoving the solids with either a centrifuge or filter.

EXAMPLE 2 Low Temperature Storage Stability Test

Stock solutions (parts by weight) are made up as follows:

    ______________________________________                                                  Stock Stock   Stock   Stock Stock                                             A     B       C       D     E                                       ______________________________________                                        Water       2000    2000    2000  2000  2000                                  Na.sub.2 SO.sub.4                                                                         --       503    --     503  --                                    Rust inhibitor:                                                               NaNO.sub.2  2.49    17.4    17.4  2.49  17.4                                  Oxidized    2.49    2.49    --    2.49  2.49                                  Petrolatum                                                                    (ALOX 1843)                                                                   Triethanolamine                                                                           7.47    --      --    7.47  --                                    Borax       --      7.47    7.47  --    7.47                                  Coagulant*, 3.74    3.74    3.74  3.74  3.74                                  Polyacrylamide                                                                polymer                                                                       (Hercofloc 831-2)                                                             ______________________________________                                         Can be replaced with any one of Hercofloc ® 847, Nalco ® 7763,        7744A, and 8800, and Nalcolyte ® 607 and 670.                        

Stock B, Stock D, and a mixture of equal parts by weight of stocks A andD were cooled in an ice bath (10-15 degrees F.) to 40 degrees F. Noapparent precipitation occurred. However, when the solutions werestirred at the same temperature, precipitation occurred immediately. Itwas determined that with agitation the sodium sulfate contained in thesesamples began to settle out about 58 degrees F. By the same test, amixture of 20 parts by weight ammonium sulfate with 80 parts by weightof Stock A was storage stable and did not crystallize out with agitationwhen the temperature was lowered to 28 degrees F. These results showthat the composition according to the invention is stable at freezingtemperature whereas comparable sulfate compositions (lacking ammoniumsulfate) are not stable even at temperatures well above the freezingpoint of water.

Low Temperature Storage Recovery

(a) Clear Stock D solution (400 g.) in a 500-ml. Erlenmeyer flask, wascooled to 45 degrees F. in an ice bath at which temperaturecrystallization and settling out took place with stirring. The mixturewas allowed to warm to room temperature and a portion of the resultingcloudy solution was added to a 5% aqueous solution of barium chloride.The resulting barium sulfate precipitate was coagulated and settled outbut the supernatant liquid was still cloudy.

(b) A 20% by weight solution of ammonium sulfate in Stock A solution wasmade up and a portion added to a 5% aqueous solution of barium chloridewith stirring. The resulting barium sulfate precipitate coagulated andsettled out leaving a clear supernatant liquid. The temperature waslowered to 28 degrees F. under agitation and no crystallization wasnoted.

(c) A second 20% by weight solution of ammonium sulfate in Stock Esolution was made up and, when cooled and agitated, did not freeze at 28degrees F. When warmed to room temperature, the solution was completelyclear. When the latter was used to precipitate barium from a 5% aqueoussolution of barium chloride, the resuting barium coagulate separatedcleanly, and the supernatant liquid was completely clear.

These results show that the solution containing sodium sulfate wasunstable at low temperature and, after a single cooling cycle, failed toregain its original clarity. The results also show that compositions ofthe present invention embodying different rust inhibitor systems arestorage stable at low temperature, and have a good regain from lowtemperature both as to retention of clarity and as to efficiency ofseparation of barium insolubles.

While the invention is described in detail in the foregoingspecification, it will be realized by those skilled in the art thatconsiderable variation can be made in such detail without departing fromthe spirit and scope of the claims which follow.

I claim:
 1. The method of treating barium-toxic waste water comprisingthe steps of mixing an aqueous composition with the waste water in anamount sufficient to enable prompt settling out of barium as solid phaseparticulates in the thus treated water and separating the particulatesfrom the water as solid waste, the composition consisting essentially ofa non-viscous solution of about 15 to 40% by weight of ammonium sulfateand about 0.0005 to about 0.15% by a water-miscible polyacrylamidepolymer agent for coagulation of non-ionic barium, the ammonium sulfatebeing present in a concentration such that the composition is storagestable at temperatures below 32 degrees F.
 2. The method according toclaim 1 where the composition contains about 1% by weight of rustpreventative.
 3. The method according to claim 2 where the rustpreventative comprises sodium nitrite.
 4. The method according to claim2 where the rust preventative comprises a soluble borate salt.